The present invention relates to a ball-point pen.
Ball-point pens are well known and widely used as writing tools, and each comprise a writing ball rotationally held in a penpoint tip. An ink filled in an ink reservoir fixed in the ball-point pen will be guided in use to the writing ball so as to be transferred to a paper, sheet or the like, as the ball rotates.
The prior art penpoint tips have been constructed such as shown in FIGS. 6(a) and 6(b). Each tip consists of a tip body 100 and a writing ball 102, and this body 100 has a distal end 101 of a conical shape. The writing ball 102 held in a ball chamber 103 is gripped with the annular distal end 101.
In detail, the interior of the penpoint tip is as follows. The ball chamber 103 formed as a cavity is disposed in a distal region, and an ink inlet opens at a proximal end of the penpoint tip. A thin axial bore 110 is in fluid communication with both the ball chamber 103 and the proximal ink inlet. Several radial grooves 107, usually called xe2x80x98spoke-likexe2x80x99 grooves, are formed in a seat 105 for supporting the ball fitted in this chamber 103.
Those radial grooves 107 in the prior art ball-point pens have each been of a width of 0.14 mm or less. A clearance between the outer spherical surface of the ball 102 and the inner peripheral wall of the chamber 103 has been 15 xcexcm or less.
Oily inks have been employed particularly for use with such ball-point pens. Recently, some types of novel ball-point pens are also known which are filled each with an aqueous thixotropic ink. These thixotropic inks have such a characteristic feature as varying in viscosity as they flow.
Each of these thixotropic inks is of a high viscosity typically ranging from 100 to 2000 mPaxc2x7s while standing still, for example, within an ink reservoir. It will however show an extremely low viscosity for instance of 10 mPaxc2x7s or less when flowing through the penpoint tip. Those inks whose aqueous matrices are blended each with a thixotropic gelling agent or thickener are usually called water-soluble gel inks.
An aqueous ink composition containing a brilliant pigment, such as a glass flake pigment or a metal-coated inorganic pigment, is disclosed in the Japanese Patent Application No. 11-76868. An average particle diameter is preferably 20-50 xcexcm for the pigment in this type of aqueous ink composition. Such an ink having the newly employed brilliant pigment of the average diameter of 20-50 xcexcm dispersed in said composition has afforded much more brilliant and stereoscopic writings or membranes on an ink-applied surface, as compared with the prior art inks containing ordinary brilliant pigments.
The present applicant has repeated continuous-writing tests with use of a thixotropic one containing glass flake pigments or the like selected from the aqueous inks disclosed in the preceding Application No. 11-76868. The ordinary ball-point pens filled with this ink have, however, proved unsatisfactory due to blurs or unsmoothness appearing in the written letters or the like. Further, the penpoint became clogged in the course of writing. These inconveniences have also been found in the case of using water-soluble gel inks each containing a metallic-luster pigment such as aluminum powder, or a titanium oxide pigment.
In view of such a drawback, it is therefore desirable to provide a ball-point pen that ensures a smooth writing free from any blur, incontinuity or clogging even if filled with a thixotropic aqueous ink containing a brilliant pigment or a glass flake pigment that comprises relatively coarse particles.
Desirably, a ball-point pen comprising: a. an ink reservoir, b. a penpoint tip, c. a writing ball rotationally disposed in and partially exposed from the penpoint tip, d. an ink feed bore in fluid communication with the ink reservoir, e. a ball chamber holding the writing ball and formed in fluid communication with the ink feed bore, f. an annular seat formed in the chamber so as to support the writing ball, and g. radial grooves formed in the annular seat, characterized in that each of the radial grooves is of a width of about 0.15 mm or more, overcomes these drawbacks.